Generally seen as an innovative educational toy, the Speak & Spell played a critical role in the introduction of cost effective and power-efficient voice digitization. Speak & Spell was one of the earliest handheld, battery operated consumer devices having a keyboard and display and produced audio from digitally synthesized sound stored in replaceable cartridge ROM and played through a special digital signal processing clip. Such a technology stood as a precursor to digital voice transmission and ultimately spurred the exponential growth of digital cellular by influencing subsequent technological innovations and trends.